In engines having one or more cylinders with dual camshafts, one for actuating the engine intake valves and a second camshaft for actuating the engine exhaust valves, a cam phaser on one or both of the camshafts may be provided for adjusting within predetermined ranges the angular positions or phases of the camshafts relative to the engine crankshaft. A single cam phaser may be mounted on the exhaust camshaft of the engine or a dual cam phasing system, with independent cam phasers on the exhaust camshaft and intake camshaft respectively, may be used.
A dual independent cam phasing system allows for variable overlap of intake and exhaust valve events and hence has improved power, torque and smoothness of operation of the engine. A control system, such as a hydraulic control system, enables the operation of a dual independent cam phasing system.